ASP.NET Change the current webform

Question

I am working at a problem in ASP.NET.

I have to create 2 windows (i think that I need to make web forms, i don't know why they said windows) one is the login form, when i press ok and the username and password is ok, I need to
show my second window (webform) How can I do that?

I tried to do

  protected void Button1_Click(object sender, EventArgs e)
        {
            Form2 form = new Form2();
            form.SetFocus("id");
        }

But it gives me error

A form tag with runat=server must exist on the Page to use SetFocus() or the Focus property.

What should I do? Am i right, I have to do separate webforms for thoose windows? This is the picture from the problem that they provided

Answer 1

If you use webforms you can just use the following code to redirect to second form:

protected void Button1_Click(object sender, EventArgs e)
        {
                 Response.Redirect("Webform2.aspx");
        }